Referring to FIGS. 12 and 13, a conventional chuck apparatus including a socket 80 and a collar 90 movably mounted on the socket 80. The socket 80 includes a closed end for connection with a motor (not shown) and an open end for receiving a tool bit 94. A ball detent 92 is put in a hole (not numbered) transversely extending the socket 80. An internal edge of a ring 99 is put in an annular groove defined in an external face of the socket 80. The collar 90 defines, in an internal face, an annular groove 91 and an annular groove 96 separated from the annular groove 91 by means of an annular rib 97. A spring 93 is put in the annular groove 96, and compressed between the annular rib 97 and the ring 82. A ring 98 is fit in the collar 90 for abutment against the ring 82, thus avoiding the collar 90 escaping from the socket 80. Referring to FIG. 12, the collar 90 is pushed downward with one hand so as to allow the ball detent 92 to enter the annular groove 91, i.e., allow the ball detent 92 to leave the annular groove 95. Thus, the tool bit 94 can be inserted in the socket 80 with the other hand. Referring to FIG. 13, the collar 90 is released. The annular rib 97 is pushed upward by means of the spring 93 supported on the ring 82. The  annular rib 97 pushes the ball detent 92 into an annular groove 95 defined in the tool bit 94, thus locking the tool bit 94 to the chuck apparatus. Referring to FIG. 12, the collar 90 is pushed downward with one hand in order to allow the ball detent 92 to enter the annular groove 91, i.e., allow the ball detent 92 to leave the annular groove 95. Thus, the tool bit 94 can be removed from the chuck apparatus with the other hand. This operation is however troublesome. There is a tool bit with a first section for driving a screw and a second section for drilling a countersink hole. The first section of the tool bit includes a screwdriver. The second section of the tool bit includes a drill and two blades. This conventional chuck apparatus however cannot receive the second section of the tool bit.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art.